Alien is a program that converts between the rpm, dpkg, stampede slp, and slackware tgz file formats. If you want to use a package from another distribution than the one you have installed on your system, you can use alien to convert it to your preferred package format and install it.
Despite the large version number, alien is still (and will probably always be) rather experimental software. It has been used by many people for many years, but there are still many bugs and limitations.
Alien should not be used to replace important system packages, like sysvinit, shared libraries, or other things that are essential for the functioning of your system. Many of these packages are set up differently by Debian and Red Hat, and packages from the different distributions cannot be used interchangably. In general, if you can’t uninstall the package without breaking your system, don’t try to replace it with an alien version.
You can install alien itself from the Ubuntu Universe repository by adding the repository to your list of sources and doing:
$sudo apt-get install alien
and then you can install the .rpm file using:
$sudo alien -k name-of-rpm-file.rpm
Try reading the alien manpage for more details on how to install other kinds of packages and the options available.
